Abstract The clinical utility of opioids for pain treatment is limited by its risk for developing opioid usage disorders (OUD). These untoward effects impose a severe burden on society and present difficult therapeutic challenges for clinicians. We propose to extend our cerebral organoid MPS to facilitate the investigation of neuronal response to opioids and identify cellular and molecular signatures in patients vulnerable to OUD. We have assembled a team with complementary expertise in clinical characterization of OUD, cerebral organoid MPS modeling, single cell RNA- seq technology, and functional characterization of neurons in mesolimbic reward system to test the hypothesis that midbrain MPS is a clinically relevant pre-clinical model for study of opioid usage disorder.